High levels of lead in the blood may be linked to behavioural and developmental problems in some children, scientists say.

Researchers from South and West Devon Health Authority found children with such problems had significant amounts of the metal - some even had above toxic levels.

They say these findings mean any child whose behaviour or development gives cause for concern should have their levels of lead tested.

Lead is a known to cause damage to nerves, but its effects can be treated.

We need to find out where the kids are getting the lead from

Harevey Marcovitch, Archives of Disease in Childhood

It can enter the body by inhalation or ingestion.

Children absorb over three times as much lead as adults because they chew objects and suck their fingers.

This study did not look at whether lead caused the behavioural problems, but said it would further contribute to their impairment.

Toxic levels

Routine blood samples were taken from 69 children who had been referred to the Child Development Centre in South West England.

They had been referred because they were getting behind in speech and language development, which could lead to educational problems - or they had a behaviour problem like hyperactivity.

Samples were also taken from 136 children who were admitted to the local district general hospital for routine surgery.

Analysis showed that children with behavioural and developmental problems had significantly higher levels of lead in their blood than the other children.

Twelve per cent had levels above those defined as "toxic".

Of the children whose samples were taken in the hospital, just half a per cent had above toxic levels.

The study's findings could not be accounted for by differences in age, sex or socioeconomics.

Susceptibility

Writing in the journal Archives of Disease in Childhood, the researchers led by Dr Gill Lewendon said: "Given that inexpensive and simple control measures have been shown to be effective in reducing children's blood lead concentrations, we feel that consideration should be given by clinicians as to whether they should be routinely requesting a blood lead [test] in children referred to them for developmental and behavioural difficulties."

Harvey Marcovitch, editor of the journal, said: "In this country we haven't really paid much attention to lead for a number of years. Really, we sort of lost interest."

He said US research had shown a link between high lead levels and low IQ, but this was the first time a link had been shown between lead and behaviour problems.

Mr Marcovitch added the next stage of research needed to look at whether lead was the cause of the behaviour problems, or if the children's habits cause them in some way to absorb more lead.

He added: "We need to find out where the kids are getting the lead from."